Washington — A key economic adviser on President Obama’s health-care reform law appeared before a congressional oversight committee on Tuesday and repeatedly sought to distance himself from recorded comments that the law relied on the “stupidity of the American voter” to win ultimate passage.

Jonathan Gruber, an economist at the Massachusetts Institute of Technology in Cambridge, was also quoted as saying that the legislation was deliberately written with “tortured language” to ensure that congressional budget experts wouldn’t identify the legislation as a tax.

Calling the legislation a tax would make it impossible to win passage, the professor had suggested.

He also said that if Americans understood the basic economic trade-off in the health-care law – that young, healthy people would be subsidizing the coverage of older, chronically ill people – the law would have never passed.

The comments were made in a series of speeches and panel discussions in the years since the 2010 passage of the Affordable Care Act. Videotapes of those appearances are being cited by Republican opponents of the ACA as proof that the Obama administration and Democratic supporters engaged in deceptive tactics to enact the controversial law.

The president and many Democrats have sought to play down Mr. Gruber’s role in formulating the ACA.

In a statement to the committee, Gruber called his comments “glib, thoughtless, and sometimes downright insulting.”

He said he was appearing before the committee to offer a full accounting of his conduct.

“I would like to begin by apologizing sincerely for the offending comments that I made,” Gruber testified. “I am not an expert in politics and my tone implied that I was, which is wrong.”

The Republican chairman of the committee, Rep. Darrell Issa of California, told Gruber he had not called the economist to Congress to berate him. He then asked: “Are you stupid?”

“I am not,” Gruber replied.

“You are a smart man who said some really stupid things?”

“The comments I made were really inexcusable,” Gruber said.

Representative Issa said that many of Gruber’s critical comments seemed to be spot on, despite his attempts now to walk them back.

Rep. Elijah Cummings of Maryland, the senior Democrat on the committee, told Gruber that his comments had made it easier for Republicans to attack the ACA.

“You gave opponents of the ACA a great gift, wrapped up in a bow,” he said.

During heated questioning from Republicans, Gruber repeatedly said he engaged in inappropriate “conjecture,” and brushed aside many pointed inquiries by saying his recorded comments were simply “glib.”

Late in the four-hour hearing, Rep. Cynthia Lummis (R) of Wyoming asked Gruber whether he really believed the statements he made in various speeches and meetings with his fellow economists. “Were all of your prior statements a lie, or were they just glib?” she asked.

Representative Lummis told Gruber that she and her husband had twice tried to sign up for Obamacare, but were twice told they had not successfully negotiated the process. In the meantime, Lummis’s husband was scheduled to take a battery of tests for chest pain.

In the resulting confusion, she said, her husband failed to take a key test. In late October, he had a heart attack and died.

Even with all the glitches and other problems, the health-care law carries “real consequences for real people,” Lummis told the economist.

Gruber’s controversial comments emerged in relation to a murky section of the ACA dealing with tax credits issued to low-income consumers who buy health insurance through health-care exchanges.

One section of the law appears to say that tax credits can be awarded only in health exchanges set up by state governments. In the years since passage of the ACA, only 16 states have set up such exchanges.

The federal government has set up exchanges in the remaining states, but it remains unclear whether the ACA authorizes tax credits under those federal exchanges.

The issue is at the center of a dispute set to be argued next year at the US Supreme Court. Those challenging the law argue that the statute was written to establish an incentive to force the states to participate in the health-care reform effort.

Government lawyers argue that the law is meant to help low-income consumers buy insurance with tax credits and that it shouldn’t matter whether the insurance is purchased under a state exchange or one set up by the national government.

During the litigation, a January 2012 videotape of a Gruber panel discussion emerged in which he appeared to endorse the restrictive view of the law being argued by the ACA opponents.

In his testimony on Tuesday, Gruber said that the videotaped remarks do not represent his complete position on the law. He said his earlier comment “omits a critical component of the context in which I was speaking.”

He added: “The point I believe I was making was about the possibility that the federal government, for whatever reason, might not create a federal exchange.”

“If that were to occur, and only in that context, then the only way that states could guarantee that their citizens would receive tax credits would be to set up their own exchanges,” he said.